$ { {-5} \times \left[\begin{array}{rr}{-1} & {2} \\ {0} & {-1} \\ {-1} & {-2}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-5}\times{-1} & {-5}\times{2} \\ {-5}\times{0} & {-5}\times{-1} \\ {-5}\times{-1} & {-5}\times{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{5} & {-10} \\ {0} & {5} \\ {5} & {10}\end{array}\right]}$